Unauthorised debit

I pay by debit order. Noticed last month it was up by R50. Queried this increase. 10 days later get a response. TRSS added the R50 for a fire service. Apparently they sent out a notice in November about this service. I did NOT respond. Because I did not not respond TRSS ASSUMED that I want the service and start to bill me, WITHOUT MY CONSENT. In my opinion this is simply *****ulent.